Treatment of hydroxyl-containing interpolymers of ethylene



Patented July 9, 1946 2,403,485 TREATMENT OF BYDROXYL-CONTAINING INTERPOLYMERS OF ETHYLENE Donald Cargill Pease, Wilmington, Deb, assignor to E. I. du Pont de Nemours 8: Company, Wilmington, M, a corporation of Delaware No Drawing. tpplicatlon December 18, 1942,

erialNo.4

11 Claims. (CL 26042) This invention relates to polymeric materials and more particularly to the treatment of hydrolyzed interpolymers of ethylene and vinyl compounds containing organic .groups hydrolyzable to hydroxyl groups whereby to term polymeric materials having generally improved physical characteristics.

An object of this invention is to provide a new class of filmand filament-forming polymeric materials.

Another object is to provide a new class of polymeric materials derived from hydrolyzed interpolymers oi ethylene and a vinyl compound containing organic groups hydrolyzable to hydroxyl groups, said polymeric materials having higher melting points, lower water-sensitivity, lower solubility in organic solvents and generally improved physical characteristics over the hydrolyzed interpolymers from which, they are derived.

A further object is to treat hydrolyzed interpolymers oi: ethylene and a vinyl organic ester to increase the melting point, to decrease the watersensitivity, to decrease the solubility, and to improve the properties thereof generally.

These and other objects will more clearly appear hereinafter.

The above objects are accomplished by my invention which, briefly stated, comprises reacting hydrolyzed interpolymers of ethylene and a vinyl organic compound in which less than 45% of the carbon atoms of the polymer chain are attached to groups from the class consisting of hydroxyl groups and organic groups hydrolyzable to hydroxyl groups (i. e., ester, ether, and acetal groups), with compounds having a plurality of methylene groups each of which is attached to nitrogen and oxygen.

The hydrolyzed polymer preferred in the prac-v tice of the present invention is that formed by the hydroylsis of the interpolymer of ethylene with an organic ester such as vinyl acetate, and the invention will be further illustrated with speciiic reference to this interpolymer although it is to be understood that my invention is applicable as well to the treatment of all hydroxyiated interpolymers of ethylene and vinyl compounds wheremonium persulfate or benzoyl peroxide at tomperatures generally above 60 to 75 C. After several hours the polymer is taken out of the reaction vessel and unreacted vinyl acetate is steam distilled off. Hydrolysis of these polyesters is carried out by dissolving them in alcohol or a tolueneor benzene-alcohol mixture, and adding an alcoholic solution of sodium or potassium hydroxide. Systems containing a substantial amount 01' water are also useful for the hydrolysis. After hydrolysis has proceeded to the desired extent. the solvents are steam distilled and the residual polymer washed and dried.

The molar ratio of ethylene to vinyl acetate in the interpolymer must be greater than 139 to satisfy the requirement that less than 45% of the carbon atoms of the polymer chain be attached to hydroxyl groups and organic groups hydrolyzable to hydroxyl groups. The preferred range of mole ratios is from 5:1 to 1:3, corresponding to from 8/:;% to 3'7%% of the carbon atoms attached to hydroxyl groups.

For most purposes it is desirable to use a prod not that is hydrolyzed to the extent of (lo-100%. In the event that the ultimate use requires a high degree of pliability, a product hydrolyzed about 75-85% is preferred, since the residual ester in less than 45% ot the carbon atoms or the polymer chain are attached to hydroxyl groups and groups hydrolyzable to hydroxyl groups, whether the interpolymer is formed from vinyl organic esters, ethers or acetals, or other suitable intermediates.

The polymerization oi the monomeric ethylene and vinyl acetate can be carried out in aqueous emulsion in the resence of catalysts such as amgroups provide a relatively permanent plastlcizing action. On the other hand, for a use demanding an ultimately higher stiffness and/or tensile roperties, it is recommended that the polyesters be hydrolyzed 95-10095.

The compounds characterized by having plurality of methylene groups, each of which isattached to nitrogen and oxygen, and hereinafter termed "reactive modifying agent, are represented by the following examples: dimethylolurea and its various others such as N,N'-bis-(methoxymethyl) urea, the aldehyde condensation products of triazine with at least two methylene groups, each of which is attached to nitrogen and oxygen, such as trimethylol melamine and the alkyl others of trimethylol melamine, poly-N- methylol derivatives of such polyamides as succinamide and adipamide, and monocyclic ureas having on each of the urea nitrogens a substituent of the formula --CH2OR such as N,N'-bis- (methoxymethy!) uron. While amounts up to 50% by weight, based on the weight of the hydrolyzed interpolymer, of these compounds give substantial modification of the hydroxyl-containing polymer, I prefer to use from about 0.1% to about 30% by weight of the reactive modifying 3 hydrolyzed inter-polymer. e. g. hydrolyzed ethylene-vinyl acetate interpolymer, and the reactive modifying agent, together with a suitable oondensation catalyst such as hydrochloric or toluenesulfonic acid, are intimately associated in a volatile organic solvent medium. The resulting composition is then cast into film or converted into any other desired form by a suitable casting. extrusion, or molding operation carried out at the lowest possible practical working temperature. Thereafter the organic solvent is removed and the treatment is completed by subjecting the solvent-free composition to temperatures oi i'rom 70 to 200 C. for a period of time suflicient to produce a high-melting. insoluble product, usually from about 1 to 3 hours.

The following examples further illustrate the invention. Parts are by weight, and the several terms and tests therein employed are defined as iollows:

"Cold crack temperature" is determined by fitting a sample of film approximately 3/ x 2" in the open jaws oi a wooden test tube holder and immersing in a cooling bath of known temperature. After one minute a trigger is released, causing the jaws oi the holder to strike sharply on a 180 fold in the sample. The temperature at which the first perceptible break is made in the sample is termed the cold crack temperature.

Melting point" is the temperature at which a film has zero tensile strength.

Mar temperature" is the temperature to which films need be heated in order to accept a permanent imprint when pressed between the forefinger and thumb.

"Tack temperature is the temperature to which a folded sample of film need be heated in order to stick together when pressed between the thumb and forefinger.

"Stifi'ness" in lbs/sq. in. is equal to the stress in pounds exerted upon a film at 1% elongation divided by lion of the cross sectional area in square inches of the unstretched film.

Pliability is 10 times the reciprocal of the stiil'ness.

"Flex durability values are obtained on the Schiltknecht flex machine. The test consists in bending a 3" x 2" piece of film into the form of a cylinder and collapsing and restoring the cylinder longitudinally at a rate of about 400 cycles per minute. The sample is inspected periodically and the flex durability is taken as the number of cycles necessary to crack the film,

Example I To a solution of 15 parts of a hydrolyzed ethylene-vinyl acetate interpolymer having a mole ratio oi 1:12, 87% hydrolyzed (22% of the carbon atoms of the polymeric chain attached to hydroxyl and attached to acetoxy groups) in 85 parts of toluene-ethanol 1:1 mixture is added 2 parts of dimethylolurea and 0.035 part of hydrochloric acid. A film is cast by flowing this solution on a smooth surface and evaporating the solvent at room temperature. After baking at 100 C. for 1 hour, the unsupported film has a melting point of over 200 C., tack temperature of 88 C., mar temperature of 114 C., cold crack temperature of -13 C., tensile strength oi 3000 lb./sq. in. with 165% elongation, and a pliability of 181. A control sample of film unmodified by reaction with dimethylolurea has a tenacity or 3300 lbs/sq. in. with elongation of 340%, pliability of 121, melting point of 120 C., tack temperature 76 C., mar temperature 99 C., and cold filmwasbakedunderaninfraredlampiorti hour. It still remained insoluble after 10 minutes in boiling toluene/ethanol (1:1) mixture while control film dissolved in this hot solvent mixture in less than one minute.

Example II A hydrolyzed ethylene-vinyl acetate interpolymer having a mole ratio of 2.9: 1, 83% hydrolyzed (11% of the carbon atoms of the polymer chain attached to hydroxyl groups and 2% attached to MCtOXY groups) is pressed into films at 150 C. The film is soaked in a solution composed 0! 95 parts of dioxane. 5 parts of N,N'-bis(methoxymethyDuron and 0.05 part 01 toluene suli'onic acid for 15 hours at 25 C. The dried film is baked 2 hours at 70 C. After one month at 25 C., it is found that the melting point is above 300 C. The treated film has a. tenacity of 3000 lbs/sq. in. with 200% elongation, and a pliability of 110. Films of the same composition that had not been chemically altered by reaction with N,N'- bis-(methoxymethylluron have a tenacity of 3500 lbs/sq. in. with 400% elongation and a melting point 01' 98 0.

Example III Ten parts of a completely hydrolyzed ethylenevinyl acetate interpolymer, having a mole ratio of 1:23 (35% 01' the carbon atoms in the polymer chain attached to hydroxyl groups) is swollen at the boiling .point of a mixture 01' toluene and ethanol (1:1). One part of N,N'-bis(methoxymethylluron and 0.1 part of diethylmethylsulfonium iodide is added to this mixture with stirring after which the solvents are allowed to evaporate at room temperature. After drying at 00 C. for 12 hours, the mixture of interpolymer, reactive agent and catalyst is heated in a mold under 50 lbs/Sq. in. pressure for 2 hours at 185 C. The product has a melting point above 250 C., and at room temperature possesses a tough, rubbery character. Moldings oi the polymer which have not undergone this reaction just described have a melting point of 180 C. and are quite stiff and brittle. Larger proportions of N,N'-bis) methoxymetyl) uron as used in this reaction yield products having increased stiffness and high melting points. 1

Example IV To a solution or 50 parts of hydrolyzed ethylene-vinyl acetate'lnterpolymer having a mole ratio of 3.6:1, 90% hydrolyzed (9.9% of the carbon atoms in the polymer chain attached to hydroxyl and 1.1% attached to alcetoxy groups), dissolved in 300 parts of 1:1 toluene-ethanol mixture is added 15 parts of N,N'-bis(methoxymethyl)urea. Films are cast from this solution more easily than those containing no modifying agent. After baking at -85 C. for 1% hours the film modified with N,N'-bis(methoxymethyl)urea had a melting point of 160 C., cold crack of 45 C., tack temperature of 75 C., and mar temperature of 70 C. The control unreacted films have a melting point of 93 C., cold crack temperature of -5 C., tack temperature of 73 C. and mar temperature of C.

Example V Sixteen parts of a hydrolyzed ethylene-vinyl acetate inter-polymer having a mole ratio of 1.6:1, 83% hydrolyzed (16% of the carbon atoms 01' the polymer chain attached to hydroxyls and 3% asoases 5 attaehedtoscetoxygroupsi,isdissolvedini parts ol toluene-ethanol 1:1 mixture, 0.48 part of dimethylolurea is added to the solution with stirring and Just belore films are cast there is added 0.02 part of ammonium dihydrogen phosphate. Alter drying the like is baked one hour at 100 C. The product of the chemical interaction of dimethylolurea and the polyalcohol has a tenacity of 8000 Ilia/sq. in. with an elongation of 250%, pliability oi 85. cold crack temperature of -20 0., and melting temperature over 200 C. A control iiim that has not been subjected to this chemical reaction has a tensile strength of 1000 lbs/sq. in. with 220% elongation, pliability 87, cold crack 0' 0., and a melting point of 80 C.

Emmple VI Eight parts 0! hydrolysed ethylene-vinyl acetate inter-polymer having a mole ratio of 3:1, 03% hydrolyzed (10% oi the carbon atoms in the polymer chain attached to hydroxyls and 2.0% attached to acetoxy groups). is dissolved in 50 parts of hot benzene-ethanol (1:1) mixture.

0.24 part of dimethylolurea is added, and lust Example 'v n A hydrolyzed ethylene-vinyl acetate interpolymer having a mole ratio of 1.6:1. 00% hydrolyzed (17% of the carbon atoms in the polymer chain attached to hydroxyl groups and 2% attached to acetoxy groups) mills to a smooth sheet on even speed rolls at 00 0.. but the temperature tially higher melting points and decreased solubility. It is quite unexpected that these modifying agents would so considerably enhance the properties of hydrolysed ethylene-vinyl acetate interpolymers that possess lewer reactive hydronl groups than polyvinyl alcohol when the same modifying agents confer far less improvements upon the letter.

A variety of methods are available for ineorporating into the hydrolyzed ethylene-vinyl acetate lnterpolymers reactive modifying agents having a plurality of methylene groups, each of which is attached to nitrogen and oxygen. The reactive modifying agents can be added to solutions oi the hydrolyzed ethylene-vinyl acetate interpolymers in organic solvents; the formed objects of hydrolysed ethylene-vinyl acetate interpolymer can be treated directly with the agent or solutions of it; or theagent can be worked into the polymer on conventional milling or calendering equipment. Solvents that have been used in these procedures are usually permitted to evaporate and ;he objects are baked at temperatures somewhat below those that cause their deformation. Catalysts such as sullonic acids or mineral acids or their acidic salts can be incorporated with the modifying agent or can be added later from the vapor phase or in any manner that will not extract large quantities ol polymer or modifying agent. By using temperatures that accelerate the-reaction between the hydrolysed ethylene-vinyl acetate interpolymer and the modifying agent for only short periods, it is possible to soften the polymer suiiiciently to permit it to be worked or to be formed into shapes that are rendered relatively permanent by further heat or catalytic treatment.

range is rather narrow as the polymer sticks badly at higher temperatures. This material has a mar temperature oi 70 C. and a cold crack temperature of C. A mixture of parts of this polymer and 1 part of N.N'-bis(methoxymethyl)uron and1% ammonium chloride catalyst can be successfully milled at 60 C. When this mixture is calendered on a fabric at 80 C. and baked for one hour at 100 0.. it is found to have a mar temperature of 150 C. and a cold crack of -20 C.

It is to be understood, ol course. that the above examples are lot purposesol illustration and that the invention is not limited to the exact materials and conditions therein described but is susceptible rather to considerable variation.

Thus, while the preferred mole ratio of ethylene to vinyl acetate in the ethylene-vinyl acetate interpolymer lies within the range 0! 5:1 and 1:8 (Bl/3% to 37%% of the carbon atoms in the polymer chain attached to hydroxyl groups), for some uses it is possible to secure sumcient modification by the present chemical treatment to render polymers having a ratio of ethylene/vinyl acetate 0! 40:1 (1% of the carbon atoms of the polymer chain attached to hydroxyl groups or groups hydrolyzable to hydroxyls) useful in certain applications. Furthermore. hydrolyzed ethylenevinyl acetate interpolymers having an ethylene] vinyl acetate ratio in the range of 1:3 to 1:0

The melting point of objects made from untreated hydrolyzed ethylene-vinyl acetate interpolymer having a mole ratio oi 3:1 is about 0. As the hydroxyl content of the polymer increases the melting point increases, so that a completely hydrolyzed polymer of ethylene-vinyl acetate having a mole ratio of 1:3 melts at about C. The products of the reaction between hydrolysed ethylene-vinyl acetate interpolymers and the reactive modifying agents described in this invention frequently do not melt until temperatures over 200 C. have been attained and are in every instance substantially higher melting than the corresponding untreated polymer. The increase in melting point will of course depend on the chemical composition ol the product as determined by the proportions of thereactants, i. e. polymer and reactive modifying agent, the conditions i'or chemical reaction. ethylene/vinyl acetate ratio. and degree of hydrolysis.

Moisture absorption which normally increases with increase in hydroxyl content in the polymeric material is greatly reduced by the treatments of this invention thus advantageously yielding a product with physical properties less easily influenced by changes in humidity.

The stillness ol the final product can be adlusted by.the p p rtions of the modllying agents used. Larger proportions of the agents ordinarily lead to products with higher stillness. Substantially completely hydrolyzed ethylene-vinyl acetate interpolymer having a mole ratio ol 8:1 (12%% ot the carbon atoms in the polymer chain are attached to hydroxyls) has a dry tenacity of about 3,000 lbs./sq. in. with 300% elongation and a stillness of about 015x10 lbs/sq. in. at 00% R. H. The stillness is unchanged or may even be slightly decreased by about 1% by weight ol the modifying agent while of the same modifying agent usually doubles the stiffness. Both tenacity and stiffness increase with hydroxyl content so that by selecting the hydrolyzed ethylene/vinyl acetate ratio of the unreacted polymer and the quantity of modifying agent added, with a view to what is ultimately desired in tenacity and stiffness, it is possible to obtain useful prodnets with a considerable range in stiffness and tenacity. Substantially completely hydrolyzed ethylene-vinyl acetate interpolymer having a mole ratio of 1:3 (Wt/2% of the carbon atoms in the polymer chain attached to hydrcxyls) modified according to this invention has a tenacity of about 6,000 lbs/sq. in. with 200% elongation and a stiffness of 0.5-1.0X 10 lbs. /sq. in. at 50% relative humidity.

For such uses as fabric coatings where high pliability and low stiffness is desired, a 1:1 or higher, e. g. 3:1, composition with small amounts of modifying agent is recommended. The products of reaction from the 1:3 compositioh and larger amounts of the polyfunctional reagents have higher stiffness and tenacity, rendering them useful as unsupported objects to accept stresses in longitudinal or transverse directions.

If the hydrolyzed ethylene-vinyl acetate interpolymer containing the reactive modifying agent and catalyst has not been given sufilcient heat treatment to render it unworkable, it is possible to add other reactive agents in a plurality of after-treatments from solvents that do not remove or react with substantial amounts of agents previously added. The reaction can also be delayed by withholding catalyst until desired operations have been completed. Catalyst can then be added from the vapor phase by milling or by solvents in a manner that will not necessarily extract the desired ingredients from the, modified polymer. Furthermore, there is usually sufllcient time lag between the addition of the reactive ingredients tb the polymer and the final setting to permit working the mixture on hot rolls and adding other agents. Other substances that do not necessarily react with the polymer or the modifying agents such as dyes, pigments, sizes, weighting materials, fillers, and plasticizers such as dibutyl phthalate, tricresyl phosphate, and di butoxyethyl sebacate, can also be added either at the time that the polymer is in solution or during the period when it can be successfully Worked on hot rolls.

Hydrolyzed ethylene-vinyl ester compound interpolymers modified by the chemical interaction with the reactive modifying agents herein disclosed are useful in the manufacture of selfsustaining film for wrapping and packaging, sheeting, fibers, tubing, filaments, molding compositions, rubber substitutes, coatings for fabrics and wire, protective finishes, adhesives for plywood, paper, and textiles, bars and other unsupported massive objects, ribbons, etc.

I claim:

1. A method which comprises reactin a hydrolyzed interpolymer of ethylene and vinyl acetate, in which hydrolyzed interpolymer from 1% to less than 45% of the carbon atoms of the polymer chain are attached to groups from the class consisting of hydroxyl groups and acetate groups, with a compound having a plurality of methylene groups each of which is attached to nitrogen and oxygen, whereby to form a substantially insoluble product having a melting point substantially higher than that of said interpolymer.

2. A method which comprises reacting a bydrolyzed interpolymer of ethylene and vinyl acetate. in which hydrolyzed interpolymer from 8%% to 375 9,, of the carbon atoms of the polymer chain are attached to groups from the class consisting of hydroxyl groups and acetate groups. with a compound having a plurality of methylene groups each of which is attached to nitrogen and oxygen, whereby to form a substantially insoluhis product having a melting point substantially higher than that of said interpolymer.

3. A method which comprises reacting a hydrolyzed interpolymer of ethylene and vinyl acetate, in which hydrolyzed interpolymer from ti /3% to 37%70 of the carbon atoms of the polymer chain are attached to groups from the class consisting of hydroxyl groups and acetate groups, with a compound having a plurality of methylene groups each of which is attached to nitrogen and oxygen, in the presence of an acid condensation catalyst, whereby to form a substantially insoluble product having a melting point substantially higher than that of said interpolymer.

4. A method which comprises intimately associating a hydrolyzed interpolymer of ethylene and vinyl acetate, in which hydrolyzed interpolymer from 1% to less than 45% of the carbon atoms -of the polymer chain are attached to groups from the .class consisting of hydroxyl-groups and acetate groups, with a compound having a plurality of methylene groups each of which is attached to nitrogen and oxygen, in an organic solvent medium, evaporating said solvent and heating the solvent-free composition to a temperature of from 70 C. to 200 0., whereby to form a substantially insoluble product having a melting point substantially higher than that of said interpolymer.

5. A product produced by the process of claim 1.

6. The method which comprises intimately associating, in an organic solvent, from 0.1 to 30 parts by weight of dimethylolurea with 100 parts by weight of a hydrolyzed interpolymer of ethylene and vinyl acetate, in which hydrolyzed interpolymer from lit/ to 37% of the carbon atoms of the polymer chain are attached to groups from the class consisting of hydroxyl group and acetate groups, at least of said groups being hydroxyl groups, evaporating said solvent and heating the solvent-free composition at a temperature within the range of from 70 C. to 200 C., whereby to form a substantially insoluble product having a melting point substantially higher than that of said interpolymer.

7. A product had according to the process of claim 6.

8. The method which comprises intimately associating, in an organic solvent, from 0.1 to 30 parts by weight of N,N'-bis (methoxymethyl) urea with 100 parts by Weight of a hydrolyzed interpolymer of ethylene and vinyl acetate, in which hydrolyzed interpolymer from il /5% to WE/ of the carbon atoms ofthe polymer chain are attached to groups from the class consisting of hydroxyl groups and acetate groups, at least of said groups being hydroxylgroups, evaporating said solvent and heating the solvent-free composition at a temperature within the range of from C. to 200 0., whereby to form a substantially insoluble product having a melting point substantially higher than that of said interpolymer.

9. A product had according to the process of claim 8.

10. The method which comprises intimately associating, in an organic solvent, from 0.1 to 30 composition at a temperature within the range of from 70 C. to 200 0., whereby to form a substantially insoluble product having a melting point substantially higher than that oi said interpolymer.

11. A product had according to the process of claim 10.

DONALD 0. PHASE.

Certificate of Correction Patent No. 2,403,465.

July 9, 1946.

DONALD CARGILL PEASE It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Column 8, line 47, claim 6, for at least 50% read at least 60%; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 17th day of September, A. D. 1946.

LESLIE FRAZER,

First Assistant Gammissicnar of Patents.

composition at a temperature within the range of from 70 C. to 200 0., whereby to form a substantially insoluble product having a melting point substantially higher than that oi said interpolymer.

11. A product had according to the process of claim 10.

DONALD 0. PHASE.

Certificate of Correction Patent No. 2,403,465.

July 9, 1946.

DONALD CARGILL PEASE It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Column 8, line 47, claim 6, for at least 50% read at least 60%; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 17th day of September, A. D. 1946.

LESLIE FRAZER,

First Assistant Gammissicnar of Patents. 

